Answer:
d. The insulin receptor is phosphorylated in response to signal molecule binding, while the erythropoietin receptor does not.
Explanation:
The insulin receptor is RTK (Receptor tyrosine kinase) type of receptor which has tyrosine kinase activity. It is a hetero dimeric receptor which is made up of alpha and beta subunits. In the absence of ligand i.e. insulin it is monomeric but as soon as insulin binds, it undergoes dimerization which further leads to the auto phosphorylation on their tyrosine residue and trans phosphorylation on the tyrosine residues of other receptors. Erythropoietin receptor on the other hand belongs to JAK STAT pathway in which receptor is monomeric like insulin receptor but doesn't undergo phosphorylation on ligand binding. This receptor undergoes phosphorylation by a tyrosine kinase instead. Here, JAK is janus kniase which is an enzyme whereas STAT is a transcription factor which is activated during the signal transduction pathway.
